The prevalence of type 2 diabetes is increasing dramatically in minority adolescents in association with the increased frequency of obesity. Nevertheless, carefully controlled studies of the use of oral hypoglycemic agents have not been performed in youth with type 2 diabetes. An oral agent, Metformin, for glucose control will be studied in children with type 2 diabetes. The use of Metformin with insulin is being compared to the use of insulin alone. If the Metformin has a beneficial effect, then the insulin will be tapered to off if feasible. This study is being conducted in cooperation with the Yale Pediatric Pharmacology Research Unit (PPRU)and the NICHD PPRU network.